The 22-year-old took his goal with aplomb and the playmaker was only denied more by a superb individual display from Pompey keeper Jamie Ashdown.
Robins was quick to praise Hammill as his team recorded a third consecutive win.
He said: "I thought Adam Hammill's goal was a great goal.
"He started the move off, got the ball played back to him and he tied himself up and smashed it in.
"He had a couple of other efforts. He's a talent and at the moment he's on fire.
"He's adding things to his game all the time - hopefully he will stay with us until he's ready to go somewhere else."